Low voltage drive systems have a competitive market with many global players. This imposes a strict low cost condition to their design. In a typical system, power-electronics components such as discrete or integrated (i.e. module type) semiconductor devices, inductors, resistors, capacitors and copper bus-bars are assembled in close proximity. PCB panels and control electronics are also present in all designs. During operation, these components dissipate heat of varying quantities. In addition, these components are tolerant to temperatures of varying levels. The environmental conditions surrounding the drive system also varies in terms of air temperature, humidity, dust and chemical content. The thermal management and integration concept of a drive system has to consider all of these underlined factors in addition to the electrical performance of the system.
Semiconductor components and power resistors are commonly built with a plate-mount design to be bolted or pressed onto a flat surface that is kept at a suitably cold temperature. Fan-blown-air cooled aluminium heat sinks and pumped water cooled cold plates are typical examples of such heat exchange surfaces. Other components such as inductors, capacitors and PCB circuit elements are typically cooled by air-flow.
Typically, components such as the choke inductors, aluminium heat sinks and DC-link capacitors are allowed to protrude on one side of a drive system whereas the more delicate components are collected on the other side. The cooling air from the fan flows through the capacitors, heat sink and the choke which have temperature limitations in the reverse order (e.g. capacitors need to be kept colder than the choke). The delicate components can be further enclosed and cooled via an additional fan in the higher IP rated versions.
The degree of environmental protection that is offered by an electronic product is commonly expressed in terms of its “Ingress Protection (IP) Rating”. Many drive products are offered in IP20 or IP21 as standard with IP54 or higher protection ratings offered as optional. With lower IP ratings it is possible to design for through-flow of outside air within the drive enclosure while still providing adequate protection. Air filters may be employed to reduce the particles in the air. Down-facing air-vents on the enclosure walls prevent vertical water droplets from entering. With higher IP ratings, however, separation of outside air from the inside air of the drive enclosure becomes essential. For the highest protection levels, a water-tight enclosure is necessary.
An air-to-air heat-exchanger is commonly employed in high IP rated enclosures in order to dissipate heat to the ambient while completely separating the cabinet internal and outside air volumes. Heat-pipes and thermoelectric cooling elements are also used in such devices.
EP 0 409 179 A1 shows a heat pipe for computers with a conduit, which comprises an exterior and interior wall, which separates the evaporator and condenser tube. The device is only intended for a horizontal position of the evaporator section and the heat producing element.
In US 2007/0133175 a heat dissipation device with a heat transfer element is shown. The heat transfer element is made in form of a base plate, which is in contact to the heat producing element and a heat pipe. The base plate comprises grooves for better contact of the heat pipes and mounting holes for mounting the plate to a substrate, on which the electronic element is mounted.